1. Field of the Invention
The present invention relates to AC power supplies for supplying power to video signal generating and transmission equipment in general and in particular to a method and apparatus comprising a filter network for providing a low and relatively stable impedance to frequencies between 80 kHz and 3.8 Mhz.
2. Description of the Related Art
As described in U.S. Pat. Nos. 5,227,962 (the "'962 Patent") and 5,260,862 (the "'862 Patent"), both of which are incorporated herein by reference, it is known that certain audio equipment is sensitive to high frequency noise induced fluctuations in the impedance of a conventional 60 Hz power source providing power to the equipment. This sensitivity can adversely affect the quality, e.g. fidelity or clarity, of and generate noise in the audio signals being propagated in the equipment. Audio equipment is also sensitive to the amount of power being delivered to the equipment. If too little power is delivered, the dynamic range of the equipment is degraded.
The '962 and '862 patents teach the use of a set of multiple series resonant circuits which are placed in parallel across the AC utility power line for audio equipment. The circuits may be configured to provide a high impedance to frequencies at and below the 60 Hz range and a low impedance above the 60 Hz range, and to increase the power factor.
Although video equipment may also be affected by noise and power factor considerations, it was not known whether a higher frequency range of noise, significantly above 60 Hz, existed on the AC utility power line, nor if such higher frequency noise would be transferred to the video equipment connected to the line. Thus, the related art did not recognize or predict that application of resonance circuits with center frequencies within specific frequency ranges, including frequencies significantly higher than 60 Hz and the audio frequency range, could be placed in parallel to the AC utility power lines for video equipment, alone or in conjunction with filters similar to those taught in the '962 and '862 patents, to achieve both an improvement in the effects of noise and a measurably brighter image.